Process of making carbonized steel for armor-plates



(No Model.)

W. E. COREY 8: F. L. SLOOUM.

PROCESS OF MAKING GARBUNIZBD STEEL FOR ARMOR PLATES. No. 574,668. Patented Jan. 5, 1897.

NVENTORS WITNESSES mm m w 9W Val/W UNITED STATES PATENT OFEIcE.

\VILLIAM ELLIS COREY, OF MUNI-IALL, AND FRANK LEROY SLOGUM, OF

PITTSBURG, PENNSYLVANIA, ASSIGNORS TO THE CARNEGIE STEEL COM- PANY, LIMITED, OF PITTSBURG, PENNSYLVANIA.

PROCESS OF MAKING CARBONIZED STEEL FOR ARMOR-PLATES.

SPECIFICATION forming part of Letters Patent No. 574,668, dated January 5, 1897.

Application filed May 28, 1896- Serial No. 593,429. (No specimens.)

To a]! Hf/MHIL it may concern:

Be itv known that we, WILLIAM ELLIs Co- REY, of Munhall, and FRANK LEROY SLooUM, of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Methods of Makin g Carbonized Steel for Armor-Plates, of which the following is a full, clear, and exact description, reference being had to the accompanying drawing, which shows in longitudinal section apparatus adapted for the prac ticc of our invention.

Our invention relates to the supercarburization of plates or pieces of steel of any size or description, but is specially designed to be applied in the manufacture of large plates or masses of steel to be forged or otherwise shaped into armor-plate.

Steel for the manufacture of armor-plates is usually made by first manufacturing the steel in any of the usual methods, but preferably by converting cast-iron into steel in the hearth of a furnace by the method known as the open-hearth process. The steel so manufactured may be alloyed with nickel, with addition of manganese, spiegeleisen, aluminium, or other metallic ingredient; and our invention is applicable to steel manufactured by any suitable process and of any desired composition of ingredients, containing such amount of carbon as may be desired, that is, the steel, before subjecting it to supercarburization, (as in the case of armor-plate) should receive a certain percentage of carbon while in the furnace and before pouring, so that an increased amount of carbon may be added on one side of the plate by the process known as supercarburization, which renders the finished plate extremely hard on one face, while it is much softer on the other face, the degree of carbon gradually increasing from the soft to the hard side, which effect has for many years been known to be the necessary result of cementation applied to one side only of a plate or mass of iron or steel, while the other side is protected from the external application of the carburizing agent.

In the recarburizing, or, as it is termed more properly, the supercarburizing, of steel, and especially in the manufacture of armor plate, it is desirable to use a sufficient degree of heat, preferably below that of the meltingpoint of cast-iron, and especially so because a high degree of heat is veryinjurious to the quality of the steel.

Our improvement is based upon the dis covery which we have made that steel plates can be supercarburized very rapidly and with improved results by heating the same with the surface to be supercarburized in contact with calcium carbid. The calcium carbid is a convenient and easily manageable reagent for the purpose. It acts much more rapidly than does free carbon in the form of charcoal, and its action on the steel is readily controllable.

The steel, having been manufactured in a suitable furnace (such, for example, as an open hearth furnace) containing 'the ordinary amount, say one-fourth of one per cent, of carbon, is cast into an ingot of suitable dimensions and then rolled or otherwise shaped into a plate of the desired form. This plate is then placed in a suitable heating-furnace, preferably a gas-furnace of suitable construc- 7 5 tion, within a suitable receptacle with refractory lining of such dimensions as to receive the steel plate and permit the application of carburizing and protecting agents.

On the bed of this receptacle is placed a layer of ground or pulverized calcium carbid of suitable depth, depending on the thickness of the steel plate under treatment. A layer containing carbid of six to eight inches in depth will suffice for a steel plate of from ten 8 5 to fifteen inches in thickness, and on this layer of carbid is laid the steel plate.

The plate maybe introduced into the furnace and deposited on the layer of calcium carbid either when the plate is cooled or, if preferred, 9c when preheated to about 1,800 Fahrenheit. The plate or plates are preferably in a horizontal position, as being more convenient when the carbid is in comminuted form. 011 the top and around the steel plate is placed 5 sand or other suitable protecting material. The receptacle thus charged is then exposed to a gradually-increasing heat in the furnace, on the hearth of which the receptacle may be permanently or removably situated. The Ice heat is gradually increased until the requisite temperature is .obtained, which should be from 1,800 to 2,10() Fahrenheit, it being necessary to raise the steel plate under treatment to a high temperature in order to enable it to absorb the additional amount of carbon required to supercarburize the steel plate. The temperature stated should be maintained in the furnace for, say, six days of twenty-four hours each, more or less, depending on the thickness of the mass of steel to be supercarburized. The heat is then gradually reduced during a further period of five days until it reaches a temperature of about 1,400 Fahrenheit, when the plate is removed from the furnace. Several steel plates may be placed in the furnace at once with layers of the carbid between the surfaces to be supercarburized.

In the accompanying drawing we show apparatus which is well adapted to the practice of our invention. Our claim, however, is not limited to the construction of the apparatus, but refers to the method herein described.

In the drawing, 2 is the heating-furnace, having ranges of gas-ports a and b on each side, through which the heating-gas is introduced on one side of the furnace and out of which it passes on the other. The direction of the gas may be reversed from time to time.

The movable hearth B is carried upon a truck C, mounted on wheels 1!, and is adapted to be moved into and out of the heating-chamber by means of a motor-cylinder (Z. This heart-h B consists of a horizontal bed 6, of brick or other refractory material, below the surface of which and extending across the hearth are flues c c, which are at such height as to coincide with the lower range of gas-ports a in the furnace, while the upper range of gasports Z) are at or about the level of the upper surface of the upper ar1norplate D. By this arrangement the heating-gas passes through the upper and lower ports a b on one side, passing through the flues under the hearth or bed B and over the top of the upper plate, whereby the furnace is suitably heated to the degree requisite or desired for treating the armor-plates, the heating-gas being supplied in the usual manner to the furnace from a generator outside.

At each end of the bed 6 of the hearth is built a temporary wall f, of such shape and size as to fit into and close the open ends of the furnace. From each side of the movable hearth B there projects an inclined flange g, of iron, which, when the truck C, carrying the movable hearth, is run into the furnace, fits against an inclined projection it h from the bottom of the inner wall of the furnace, thus closing the heating-chamber on both sides as well as at the ends.

The armor-plates D E to be supercarburized are placed in the hearth of the furnace with a layer F of comminuted calcium carbid be tween the surfaces to be supercarburized, and the carbid is protected from oxidation preferably by incasing the edges of the plates in sand 7:.

Other apparatus may be used for heating the armor-plates to be carburized on one side, and, if desired, one plate only at a time may be treated, or a series of plates may be treated in the furnace at the same time by making obvious changes in the apparatus, which we have described in this specification not for the purpose of basing any claims thereon, but for the purpose of illustrating a practical method of using our improved process.

The special advantages resulting from the use of our improvement are due to the employment of the highly-active calcium carbid, the carbon of which unites with the steel much more rapidly and efficiently than when the carburization or supercarburization of steel is effected by the ordinary processes involving the employment of animal or vegetable charcoal, or of mineral carbon, or of hydrocarbon vapor, as of petroleum, or of the ordinarycoal-gas, so that whereas in the process as heretofore practiced the time required for supercarb urizin g a steel armor-plate was about twenty-seven days, or six hundred and forty-eight hours, it can be done by our process in fifteen days, or three hundred and sixty hours.

e desire to include as equivalents under the term calcium carbid similar metallic carbids, such as the double carbid of magnesium and calcium.

lVe claim The process herein described for supercarburizin g steel for armor-plates and other purposes, which consists in heating the same with the surface to be supercarburized in contact with calcium carbid.

In testimony whereof we have hereunto set our hands.

\VILLIAM ELLIS COREY. FRANK LEROY SLOCUM. \Vitnesses as to XV. E. Corey:

\V. II. CORBETT, L. C. EAKMAN. \Vitnesses asto F. L. Slocum:

G. I. IIoLDsHIr, II. M. CoRwIN. 

